We explored the connection between vitamin D levels and upper respiratory tract infections (URTIs) among military recruits during their training. This observation spanned across different seasons and included over 1,600 recruits. Our aim was to understand how achieving sufficient vitamin D levels could potentially impact the frequency and severity of colds among physically active individuals.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
Read More
8
Vitamin D3 aids cold recovery
Intake of 25-Hydroxyvitamin D3 Reduces Duration and Severity of Upper Respiratory Tract Infection: A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study.
We explored how 25-hydroxyvitamin D3 (25OHD), a form of vitamin D, influences upper respiratory tract infections (URTIs), commonly known as colds. In a carefully designed clinical study, we followed 428 participants aged 45 to 74 over a 16-week period. They were randomly assigned to receive either 10 μg of 25OHD daily or a placebo, all while maintaining a double-blind setup to ensure accurate results.
Our findings revealed that those who took 25OHD had reduced duration and severity of their cold symptoms. Participants reported improvements in their overall quality of life during the bouts of URTI. By tracking the health of the participants through surveys designed to measure cold symptoms, we gathered valuable data that indicates vitamin D3 could play a helpful role in managing colds.
This suggests that incorporating vitamin D3 into our diets may be beneficial when we catch a cold, potentially leading to a quicker recovery. It’s a promising avenue for anyone looking to ease the discomfort and duration of these frustrating infections.
Read More
7
Vitamin D's limited cold impact
High-dose oral vitamin D supplementation for prevention of infections in children aged 0 to 59 months: a systematic review and meta-analysis.
We evaluated the impact of high-dose vitamin D supplementation, specifically doses exceeding the standard 400 IU, on preventing colds and other infections in children under five years of age. Our analysis included seven studies, involving a total of 5,748 children, which looked into how effective vitamin D might be in reducing the incidence of upper respiratory tract infections.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Read More
Most Useful Reviews
9
Boosted energy levels
I have been taking Vitamin D supplements for the past few months, and I cannot express how much of a difference it has made to my overall well-being. Living in a region with long winters and limited sunlight, I often felt fatigued. After consulting with my doctor, I decided to give Vitamin D a try. Within weeks, I noticed a significant boost in my energy levels and mood. My immune system seems stronger; I’ve avoided colds that typically would have knocked me out during the season! I appreciate the quality of this brand—it's non-GMO, soy-free, and carefully formulated.
Read More
9
Improved health overall
I have been taking this product and am very pleased with the supplement. It maintains my vitamin D levels, especially in winter when there is not enough sun. The vegan formula is important as I try to choose supplements of plant origin, and this one uses Vitashine D3, which is easily absorbed. After a month, I noticed improved overall health, more energy, and better immunity, as I haven’t had any colds or illnesses. The capsules are easy to swallow and cause no side effects. Overall, a great health supplement for those seeking quality vegan vitamin D.
Read More
9
Effective D3 source
Although there are many vegan vitamin Ds on the market, I found most to be D2, which is less effective. This one is D3, better absorbed and effective. I have been taking it for years, and it is easy to digest, with no taste, and it works great. Many people, not just vegans, are deficient in vitamin D. I take it daily and maintain optimal levels on my yearly bloodwork, despite living in a cold climate and being a vegan for over 20 years.
We explored the connection between vitamin D levels and upper respiratory tract infections (URTIs) among military recruits during their training. This observation spanned across different seasons and included over 1,600 recruits. Our aim was to understand how achieving sufficient vitamin D levels could potentially impact the frequency and severity of colds among physically active individuals.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
Read More
8
Vitamin D3 aids cold recovery
Intake of 25-Hydroxyvitamin D3 Reduces Duration and Severity of Upper Respiratory Tract Infection: A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study.
We explored how 25-hydroxyvitamin D3 (25OHD), a form of vitamin D, influences upper respiratory tract infections (URTIs), commonly known as colds. In a carefully designed clinical study, we followed 428 participants aged 45 to 74 over a 16-week period. They were randomly assigned to receive either 10 μg of 25OHD daily or a placebo, all while maintaining a double-blind setup to ensure accurate results.
Our findings revealed that those who took 25OHD had reduced duration and severity of their cold symptoms. Participants reported improvements in their overall quality of life during the bouts of URTI. By tracking the health of the participants through surveys designed to measure cold symptoms, we gathered valuable data that indicates vitamin D3 could play a helpful role in managing colds.
This suggests that incorporating vitamin D3 into our diets may be beneficial when we catch a cold, potentially leading to a quicker recovery. It’s a promising avenue for anyone looking to ease the discomfort and duration of these frustrating infections.
Read More
7
Vitamin D's limited cold impact
High-dose oral vitamin D supplementation for prevention of infections in children aged 0 to 59 months: a systematic review and meta-analysis.
We evaluated the impact of high-dose vitamin D supplementation, specifically doses exceeding the standard 400 IU, on preventing colds and other infections in children under five years of age. Our analysis included seven studies, involving a total of 5,748 children, which looked into how effective vitamin D might be in reducing the incidence of upper respiratory tract infections.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Read More
7
Vitamin D's role in Raynaud management
Serum vitamin B12 and D levels in children with Primary Raynaud Phenomenon: a retrospective cohort study.
We explored the impact of vitamin D and B12 deficiencies in children experiencing primary Raynaud phenomenon (RP), which causes temporary blood flow changes often triggered by cold or stress. Our study aimed to identify how common these vitamin deficiencies are in pediatric patients and whether they influenced the severity of Raynaud symptoms.
Out of 40 young participants, a significant portion—41.5% for vitamin B12 and 39% for vitamin D—showed low serum levels of these vitamins. After providing supplementation, we observed improved symptoms in many cases, particularly through warming techniques. However, it's important to note that while vasodilator treatment needs were generally unchanged regardless of vitamin B12 levels, those who had vitamin D deficiencies and subsequently received vitamin D treatment required significantly less vasodilator therapy.
Overall, while some positive effects of vitamin D were noted, further research is necessary to conclusively determine its role in managing primary RP symptoms and its effectiveness in combating cold-induced episodes.
Read More
7
Vitamin D reduces cold symptoms
Intake of 25-Hydroxyvitamin D May Reduce the Severity of Upper Respiratory Tract Infection: Post hoc Analysis of a Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study.
We explored the effects of 25-hydroxyvitamin D (25OHD) on individuals experiencing upper respiratory tract infections (URTIs), commonly known as colds. In a well-structured study, participants with low vitamin D levels received either a daily dose of 10 micrograms of 25OHD or a placebo for a span of 16 weeks. The participants' symptoms were assessed using the Wisconsin Upper Respiratory Symptom Survey-21, focusing on how the vitamin impacted their cold symptoms.
Our findings showed that those taking 25OHD reported significant reductions in physical symptoms such as runny noses, sneezing, and head congestion compared to those on the placebo. Additionally, the quality of life scores improved for most symptoms, except for ease of breathing. However, it’s important to note that there was no significant difference in the total number of cold events or how often participants used medications like antibiotics or pain relievers.
Collectively, these results suggest that adequate intake of vitamin D can help ease cold symptoms, particularly those affecting the nose, and might enhance overall well-being when a cold strikes. This indicates that vitamin D may play a positive role in managing the discomfort associated with upper respiratory infections.
I have been taking Vitamin D supplements for the past few months, and I cannot express how much of a difference it has made to my overall well-being. Living in a region with long winters and limited sunlight, I often felt fatigued. After consulting with my doctor, I decided to give Vitamin D a try. Within weeks, I noticed a significant boost in my energy levels and mood. My immune system seems stronger; I’ve avoided colds that typically would have knocked me out during the season! I appreciate the quality of this brand—it's non-GMO, soy-free, and carefully formulated.
Read More
9
Improved health overall
I have been taking this product and am very pleased with the supplement. It maintains my vitamin D levels, especially in winter when there is not enough sun. The vegan formula is important as I try to choose supplements of plant origin, and this one uses Vitashine D3, which is easily absorbed. After a month, I noticed improved overall health, more energy, and better immunity, as I haven’t had any colds or illnesses. The capsules are easy to swallow and cause no side effects. Overall, a great health supplement for those seeking quality vegan vitamin D.
Read More
9
Effective D3 source
Although there are many vegan vitamin Ds on the market, I found most to be D2, which is less effective. This one is D3, better absorbed and effective. I have been taking it for years, and it is easy to digest, with no taste, and it works great. Many people, not just vegans, are deficient in vitamin D. I take it daily and maintain optimal levels on my yearly bloodwork, despite living in a cold climate and being a vegan for over 20 years.
Read More
7.5
Essential for health
Vitamin D from Dr. Best is an essential vitamin for maintaining health, especially during the period of seasonal colds. A prophylactic dosage for every day for adults yields visible results.
Read More
Frequently Asked Questions
Cold is a term that refers to a state of low temperature, often associated with a perceptibly chilly environment or the sensation of being cool to the touch. Scientifically, cold is relative to the presence and movement of heat, which is a measure of energy within matter. In everyday terms, we experience cold through weather changes, such as during winter months, and it can also be described in the context of specific temperature ranges – for example, temperatures below 32 degrees Fahrenheit (0 degrees Celsius) generally signify freezing conditions, which can impact outdoor activities, personal comfort, and various ecological systems.
Moreover, the sensation of cold is not solely dependent on temperature; factors like humidity and wind chill can enhance the feeling of coldness. When discussing cold in terms of human health, prolonged exposure to cold conditions can lead to hypothermia or frostbite if body heat is not effectively maintained. Hence, it's crucial to dress appropriately and take necessary precautions during colder months to prevent adverse effects. Understanding the concept of cold can help individuals better prepare for seasonal changes and ensure their comfort and safety.
Vitamin D is a fat-soluble vitamin that's essential for maintaining healthy bones and teeth, supporting immune system function, and facilitating normal cell growth and development. It plays a crucial role in calcium absorption in the gut, which is vital for bone health. Unlike most vitamins, our bodies can produce Vitamin D when exposed to sunlight, specifically UVB rays, which is why it’s often referred to as the "sunshine vitamin." However, depending on your geographical location, lifestyle, and skin type, getting sufficient Vitamin D from the sun alone can be challenging, particularly during the winter months.
In addition to sunlight, Vitamin D can be obtained from certain foods such as fatty fish (like salmon and mackerel), fish liver oils, and fortified foods like milk and cereals. Some individuals may also consider supplements, especially if they're at risk for deficiency. Insufficient vitamin D levels are linked to various health issues, including rickets in children, osteomalacia in adults, and even an increased risk of chronic diseases. Regularly checking your vitamin D levels and consulting with a healthcare professional can help ensure you're meeting your needs for optimal health.
Vitamin D is often discussed in relation to immune health, and some studies suggest that it may play a role in reducing the risk of upper respiratory infections, including the common cold. Adequate levels of vitamin D might help enhance your immune response, potentially making your body more effective at fighting off infections. However, the evidence is not entirely conclusive, and while some individuals with low vitamin D levels may experience more frequent colds, it's important to consider that other factors also contribute to overall immunity, such as lifestyle and diet.
If you’re considering using vitamin D supplements to prevent or mitigate the effects of a cold, it’s always best to consult with a healthcare professional. They can provide tailored advice based on your specific health needs and possible deficiencies. While maintaining sufficient vitamin D levels can be beneficial for your immune system, it should not be seen as a guaranteed solution to avoid catching colds, especially during peak cold and flu seasons.
Based on user reviews, individuals typically see results from taking Vitamin D supplements for cold support within a few weeks to a month. One user reported noticing a significant boost in energy and an improved immune system after just weeks of use, stating they avoided colds that would usually affect them during the winter months Read Review. Similarly, another user mentioned that after a month of taking the supplement, they experienced better overall health and immunity, describing it as an effective choice to maintain their vitamin D levels during the winter Read Review.
Overall, these insights suggest that if you're considering Vitamin D for cold relief, you might begin to notice benefits in energy and immune function within a few weeks of consistent use. Regular dosage is key, with one reviewer emphasizing the importance of maintaining a daily regimen, particularly in climates prone to seasonal colds Read Review.
Vitamin D supplementation has shown varying effects on colds, particularly among children and adults with low vitamin D levels. Several studies, including one that assessed the impact of vitamin D on children under six, presented mixed results. While a study indicated that daily doses of 800 IU for three months led to quicker recovery from mild respiratory symptoms, many studies found no significant benefits in preventing or treating colds [1]. Furthermore, another study focusing on high-dose vitamin D supplementation reported a 57% reduction in cold occurrences among children taking over 1,000 IU daily, although the certainty of these findings was lower [2].
In adults, research has shown that individuals with sufficient vitamin D levels experienced a 40% lower likelihood of upper respiratory infections, with supplementation leading to a notable reduction in the severity of cold symptoms and the number of days affected by such infections [4]. In particular, participants noted improvements in symptoms like runny nose and head congestion while using 25-hydroxyvitamin D, suggesting that adequate vitamin D intake may alleviate cold symptoms and enhance overall well-being during illness [5]. Collectively, while the role of vitamin D in cold prevention and treatment may not be entirely definitive, there is promising evidence that it can reduce the severity and duration of symptoms, making it worth considering during cold seasons.
According to user reviews, several individuals have reported notable improvements in their symptoms after incorporating Vitamin D supplements into their routines. One user noted a significant boost in energy levels and mood within just a few weeks, attributing their enhanced immune strength to the supplement, as they successfully avoided seasonal colds that usually affected them Read Review. Another reviewer echoed similar sentiments, stating that after a month, they experienced better overall health and increased vitality, which they linked to improved immunity and an absence of illness Read Review.
Moreover, users appreciate that Vitamin D3, as found in these supplements, appears to be more effective than other forms like D2, leading to optimal vitamin levels even in challenging climates Read Review. One reviewer emphasized the importance of daily intake, noting that consistent use yields visible results particularly during colder months Read Review. While experiences may vary from person to person, these reviews suggest that those seeking to enhance their wellness and immune function, especially during winter, might find Vitamin D to be a beneficial addition to their health regimen.
Based on current research, the optimal dose of Vitamin D for treating cold symptoms appears to be around 10 micrograms (or 400 IU) daily, though higher doses may also prove beneficial. A study focusing on participants with low vitamin D levels reported significant reductions in cold symptoms when they received 10 micrograms of 25-hydroxyvitamin D (25OHD) daily over 16 weeks, resulting in enhanced quality of life and symptom alleviation compared to those on a placebo [5]. Additionally, another study exploring high-dose Vitamin D found that doses exceeding 1,000 IU daily led to a notable reduction in cold occurrences, demonstrating a 57% decrease in colds specifically [2].
While these findings suggest that maintaining adequate Vitamin D levels can help manage cold symptoms, it's important to note that not all doses or forms may lead to significant clinical benefits across the board. The evidence remains mixed; for instance, although some studies indicate potential for quicker recovery with doses around 400 IU or higher, other research has not shown a significant difference in overall infection rates. Thus, while higher doses like those surpassing 1,000 IU may reduce cold incidence, the clear ideal dosage for symptomatic relief continues to be evaluated [1].
9
Boosted energy levels
I have been taking Vitamin D supplements for the past few months, and I cannot express how much of a difference it has made to my overall well-being. Living in a region with long winters and limited sunlight, I often felt fatigued. After consulting with my doctor, I decided to give Vitamin D a try. Within weeks, I noticed a significant boost in my energy levels and mood. My immune system seems stronger; I’ve avoided colds that typically would have knocked me out during the season! I appreciate the quality of this brand—it's non-GMO, soy-free, and carefully formulated.
9
Improved health overall
I have been taking this product and am very pleased with the supplement. It maintains my vitamin D levels, especially in winter when there is not enough sun. The vegan formula is important as I try to choose supplements of plant origin, and this one uses Vitashine D3, which is easily absorbed. After a month, I noticed improved overall health, more energy, and better immunity, as I haven’t had any colds or illnesses. The capsules are easy to swallow and cause no side effects. Overall, a great health supplement for those seeking quality vegan vitamin D.
7.5
Essential for health
Vitamin D from Dr. Best is an essential vitamin for maintaining health, especially during the period of seasonal colds. A prophylactic dosage for every day for adults yields visible results.
9
Effective D3 source
Although there are many vegan vitamin Ds on the market, I found most to be D2, which is less effective. This one is D3, better absorbed and effective. I have been taking it for years, and it is easy to digest, with no taste, and it works great. Many people, not just vegans, are deficient in vitamin D. I take it daily and maintain optimal levels on my yearly bloodwork, despite living in a cold climate and being a vegan for over 20 years.
5
Vitamin D and cold symptoms
The Effects of Vitamin D Supplementation on Respiratory Infections in Children under 6 Years Old: A Systematic Review.
We explored the effects of vitamin D supplementation on respiratory infections, particularly colds, in children under six years old. By examining various studies published until February 2023, we observed diverse findings, with some studies reporting benefits while others found no significant advantage. Overall, eight studies were included, with a total of 2,189 children assessed.
While a few studies indicated that low vitamin D levels might be linked to an increased risk of respiratory infections, only one study specifically noted that children who took 800 IU of vitamin D daily for three months experienced fewer mild respiratory symptoms and recovered more quickly. However, a significant number of studies showed no notable differences in the rates or severity of colds when vitamin D supplementation was used.
In essence, the evidence regarding vitamin D's role in preventing or effectively treating colds in young children is still unclear. We did find some indications that certain doses, like 80 IU/kg/day, may help reduce acute respiratory infection risks, but most research highlighted only minor benefits, such as quicker recovery rather than preventing infections. Variability in study design and supplementation protocols contributed to these inconclusive results, highlighting the need for further research.
7
Vitamin D's limited cold impact
High-dose oral vitamin D supplementation for prevention of infections in children aged 0 to 59 months: a systematic review and meta-analysis.
We evaluated the impact of high-dose vitamin D supplementation, specifically doses exceeding the standard 400 IU, on preventing colds and other infections in children under five years of age. Our analysis included seven studies, involving a total of 5,748 children, which looked into how effective vitamin D might be in reducing the incidence of upper respiratory tract infections.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
8
Vitamin D reduces cold severity
Influence of Vitamin D Supplementation by Simulated Sunlight or Oral D3 on Respiratory Infection during Military Training.
We explored the connection between vitamin D levels and upper respiratory tract infections (URTIs) among military recruits during their training. This observation spanned across different seasons and included over 1,600 recruits. Our aim was to understand how achieving sufficient vitamin D levels could potentially impact the frequency and severity of colds among physically active individuals.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
7
Vitamin D reduces cold symptoms
Intake of 25-Hydroxyvitamin D May Reduce the Severity of Upper Respiratory Tract Infection: Post hoc Analysis of a Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study.
We explored the effects of 25-hydroxyvitamin D (25OHD) on individuals experiencing upper respiratory tract infections (URTIs), commonly known as colds. In a well-structured study, participants with low vitamin D levels received either a daily dose of 10 micrograms of 25OHD or a placebo for a span of 16 weeks. The participants' symptoms were assessed using the Wisconsin Upper Respiratory Symptom Survey-21, focusing on how the vitamin impacted their cold symptoms.
Our findings showed that those taking 25OHD reported significant reductions in physical symptoms such as runny noses, sneezing, and head congestion compared to those on the placebo. Additionally, the quality of life scores improved for most symptoms, except for ease of breathing. However, it’s important to note that there was no significant difference in the total number of cold events or how often participants used medications like antibiotics or pain relievers.
Collectively, these results suggest that adequate intake of vitamin D can help ease cold symptoms, particularly those affecting the nose, and might enhance overall well-being when a cold strikes. This indicates that vitamin D may play a positive role in managing the discomfort associated with upper respiratory infections.
References
Marusca LM, Reddy G, Blaj M, Prathipati R, Rosca O, et al. The Effects of Vitamin D Supplementation on Respiratory Infections in Children under 6 Years Old: A Systematic Review. Diseases. 2023;11. doi:10.3390/diseases11030104
Carboo JA, Dolman-Macleod RC, Malan L, Lombard MJ. High-dose oral vitamin D supplementation for prevention of infections in children aged 0 to 59 months: a systematic review and meta-analysis. Nutr Rev. 2024;82:579. doi:10.1093/nutrit/nuad082
Kisla Ekinci RM, Taskin Karacay IE, Celik U. Serum vitamin B12 and D levels in children with Primary Raynaud Phenomenon: a retrospective cohort study. Eur J Clin Nutr. 2022;76:1615. doi:10.1038/s41430-022-01151-0
Harrison SE, Oliver SJ, Kashi DS, Carswell AT, Edwards JP, et al. Influence of Vitamin D Supplementation by Simulated Sunlight or Oral D3 on Respiratory Infection during Military Training. Med Sci Sports Exerc. 2021;53:1505. doi:10.1249/MSS.0000000000002604
Shimizu Y, Ito Y, Uotsu N, Yui K. Intake of 25-Hydroxyvitamin D May Reduce the Severity of Upper Respiratory Tract Infection: Post hoc Analysis of a Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study. Nutrients. 2020;12. doi:10.3390/nu12123769
Shimizu Y, Ito Y, Yui K, Egawa K, Orimo H. Intake of 25-Hydroxyvitamin D3 Reduces Duration and Severity of Upper Respiratory Tract Infection: A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study. J Nutr Health Aging. 2018;22:491. doi:10.1007/s12603-017-0952-x